Simple high-voltage pulse generating system



Dec. 12, 1967 3,358,216

SIMPLE HIGH-VOLTAGE PULSE GENERATING SYSTEM D. J. KOSTUCH Filed Sept. 1, 1965 O .H 6 0 He G l .HV [e D U 9 %5 V k 4 ll 0 0 l3 0 5 ll Z Q B o N w v 0 M H O 5 6 O 2 3 v 6 M m VU W nm m i i C C W T O T 0 5 S o S 4 S S Input From Input Pulse Output Pulse Current in Winding I3 INVENTOR. DONALD J. KOSTUCH BY ATTORNEY United States Patent 3,358,216 LE HIGH-VOLTAGEEPULSE GENERATING ST M This invention relates to pulse generating systems and more particularly to pulse generating systems for providing high voltage pulses.

The invention finds particular utility for providing high voltage pulses to operate devices such as an electrostatic printer which utilizes the high voltage pulse to attract ink from a reservoir onto a document. The control signal for actuating the printer is applied to the high voltage pulse generating system which then develops a high voltage pulse for operating the electrostatic printer. The high voltage pulse generating system of this invention is capable of generating high voltage pulses at 500 cycles per second.

Accordingly, a principal object of the invention is to provide an improved high voltage pulse generating system.

Another important object of the invention is to provide a high voltage pulse generating system which does not consume power during a steady or idling state.

Still another very important object of the invention is to provide a high voltage pulse generating system which does not require a high voltage supply.

Yet a further important object of the invention is to provide a high voltage pulse generating system which operates at a relatively high cyclic rate.

Yet another object of the invention is to provide a high voltage pulse generating system which is simple and inexpensive.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a schematic circuit diagram illustrating the invention;

FIG. 2 is a circuit diagram for the drive circuits illustrated in block form in FIG. 1; and,

FIG. 3 is a wave form diagram.

With reference to the drawings, and particularly to FIG. 1, the invention is illustrated by way of example as including a transformer 16 having a center tapped primary winding 11 and secondary windings 12 and 13. The center tap of winding 11 is connected to a -12 volt potential source. One end of the primary winding 11 is connected to a drive circuit While the other end is connected to a drive circuit 36. The details of the drive circuits 2t and are shown in FIG. 2 and will be described shortly hereinafter. The drive circuits 2i) and 30 function to provide currents through primary winding 11 in opposite directions. Of course, only one of the drive circuits is operative at any one time.

In order to generate the high voltage pulses by means of the transformer 10, a relatively large flux change is required. This large change in flux is achieved by first applying a drive current in one direction to the primary winding to preset the core flux and a clamp circuit is provided to prevent a voltage pulse from appearing on the secondary output winding. Thereafter, a drive current is applied to the primary winding in the opposite direction. This produces a large change in fluX and the clamp circuit is reverse biased whereby a voltage is developed across the secondary output winding.

In this example, secondary winding 12 is the output winding. It is connected between ground and a utilization device 60 which is to receive the high voltage pulse. Secondary winding 13 is wound in phase opposition to Winding 12. It is connected in series with a clamping diode 14 and a dissipating resistor 15. When current flows through winding 11 from drive circuit 20, diode 14 is forward biased and substantially all the energy produced by the current flowing through winding 13 is dissipated in resistor 15. Only a small negative voltage is produced across winding 12 because most of the energy is dissipated in resistor 15. By this arrangement, drive circuit 20 is operated to preset the core flux and in this example, to a negative value. Thereafter the drive circuit 30 is operated whereby the diode 14 is reverse biased and the energy appears across the winding 12 in the form of a high voltage substantially square pulse.

Drive circuit 20 is operated for a time duration determined by the period of singleshot multivibrator 40. singleshot multivibrator 40 is fired by control signal T0 applied to input terminal 45. The control signal To can be supplied from any suitable source, such as a computer, when it is desired to generate a high voltage pulse such as for printing or marking operation. The output of the singleshot multivibrator 40 is also connected to the input of singleshot multivibrator 50 which has its output connected to drive circuit 30. Thus, when singleshot multivibrator 40 times out, the drive circuit 20 is rendered inoperative and the singleshot multivibrator 50 fires to operate drive circuit 30. The drive circuit 30 then remains operative for a time duration determined by the period of the singleshot multivibrator 50. It should be noted that after drive circuit 30 is rendered inoperative, i.e., after singleshot multivibrator 50 times out, the collapsing flux in transformer 10 forward biases the diode 14 thereby preventing backswing across winding 12 and also permitting the core flux to dissipate its energy through resistor 15.

The drive circuits 2t} and 3% are substantially identical and therefore the details of only one drive circuit are shown in FIG. 2. The output of the singleshot multivibrator 40 is connected to the input of an inverter 21 of drive circuit 26. The output of the inverter 21 is connected to the base of transistor 22 which is connected in a complementary emitter follower configuration with transistor 23. Transistor 22, its collector being connected to ground potential, is normally conducting whereby transistor 24 which has its base connected to the common emitters of transistors 22 and 23 is held non-conducting. When the singleshot multivibrator 40 is fired, the base of transistor 22 goes negative and transistor 22 switches OFF. This allows the bases of transistors 23 and 24 to become more negative and they switch ON. With transistor 24 conducting, a relatively high drive current flows through coil 11. When the singleshot multivibrator 40 times out, transistor 22 is switched ON and transistors 23 and 24 are switched OFF. This terminates the flow of current through coil 11 under control of transistor 24.

Mode 0 operation In order to have a high voltage pulse furnished to utilization device 60, the core flux of transformer 10 is first preset to a negative value as control pulse T0, FIG. 3, fires singleshot multivibrator 46, FIG. 1. With singleshot multivibrator 40 fired, drive circuit 20 is turned ON and a current flows through coil 11 toward the 12 volt center tap point for a length of time as determined by the period of the singleshot multivbrator 40, i.e., from T0 to T1, see FIG. 3. Under this condition, current flows through coil 13 because diode 14 is forward biased. Most of the energy is dissipated in resistor and thus a very small voltage pulse appears across coil 12. When the singleshot multivibrator 40 times out, the singleshot multivibrator 50 is fired whereby drive circuit 30 is rendered active from time T1 to T2 and current flows through coil 11 therefrom to the -12 volt center tap point. Thus current is flowing from drive circuit 30 through coil 11 in an opposite direction to that from drive circuit 20. There fore, diode 14 is reversed biased and the current due to transformer action now flows through coil 12 whereby a high voltage pulse is delivered to the utilization device 60. After the singleshot multivibrator 50 times out, the drive circuit 30 turns OFF and the core flux collapses. During the time the core flux is collapsing, diode 14 is again forward biased and the energy is dissipated in resistor 15.

Summary From the foregoing it is seen that the invention provides high voltage pulses without the need of a high voltage supply. Further, it is seen that the circuit for providing these high voltage pulses is relatively simple and inexpensive. It is also seen that during the time a high volt age pulse is not generated, both drive circuits are OFF and therefore no power is consumed during the steady or idling state and therefore safety and economy are achieved.

Although two separate drive circuits are shown, it is possible to use a bi-lateral current driver. However, such an arrangement is more complex than the two drive circuits.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. Apparatus for generating high voltage pulses comprising:

a transformer having a core wound with a primary winding and first and second secondary windings, said first and second secondary windings being wound 180 in phase opposition;

a clamp circuit connected in series with said second secondary winding to facilitate presetting the core flux, said clamp circuit including an impedance for dissipating energy; and

means connected to said primary winding for driving current therethrough first in one direction to preset said core flux whereby current flows through said second secondary winding under control of said clamp circuit and the energy is dissipated by said impedance, and then in an opposite direction to cause a core flux change to produce a high voltage pulse across said first secondary winding, said clamp circuit then being operative to prevent flow of current through said second secondary winding.

2. Apparatus for generating high voltage pulses comprising:

a transformer having a core wound with a primary winding and first and second secondary windings, said first and second secondary windings being wound 180 in phase opposition;

a clamp circuit connected in series with said second secondary winding to facilitate presetting the core flux and including an impedance for dissipating energy;

first and second drive circuits connected to said primary winding to drive current therethrough successively in opposite directions; and

means for sequentially operating said first and second drive circuits whereby current is first driven through said primary Winding in one direction to preset the core flux as current flows through said second secondary winding under control of said clamp circuit and then driven through said primary winding in an an opposite direction to cause a flux change as cur rent flows through said first secondary winding to produce a high voltage pulse thereacross.

3. The apparatus of claim 2 wherein said means for sequentially operating said first and second drive circuits comprises first and second singleshot multivibrators with the output of said first singleshot multivibrator connected to said first drive circuit and to the input of said second singleshot multivibrator and the output of said second singleshot mul-tivibrator being connected to the input of said second drive circuit.

4. The apparatus of claim 2 wherein said clamp circuit consists of a diode connected in series with said second secondary winding and said impedance comprises a resistor connected in series with said diode and said second secondary winding.

5. Apparatus for generating high voltage pulses comprising:

a transformer having a core Wound with a center tapped primary winding and first and second secondary windings, said first and second secondary windings being wound in phase opposition;

a clamp circuit connected in series with said second secondary winding to facilitate presetting the core flux and including an impedance for dissipating energy; and

means connected to said center tapped primary winding for driving current through one portion of said primary winding to said center tap thereof to preset said core flux and then drive current through the other portion of said primary winding to the center tap thereof whereby as current flows through said first portion of said center tapped primary winding said clamp circuit permits current to flow through said second secondary winding and the energy is dissipated in said impedance and as current flows through said other portion of said center tap primary winding said clamp circuit prevents current from flowing in said second secondary winding and current flows through said first secondary winding and a high voltage pulse is developed thereacross.

6. The apparatus of claim 5 wherein said current driving means comprises a first drive circuit connected to one end of said center tapped primary winding;

first triggering means connected to trigger said first drive circuit;

a second drive circuit connected to the other end of said center tapped primary winding; and

second triggering means connected to said first triggering means and to said second drive circuit and operative in response to said first triggering means be coming inoperative for activating said second drive circuit.

7. Apparatus for generating high voltage pulses comprising:

a transformer having a core wound with a center tapped primary Winding and first and second secondary windings, said first and second windings being Wound 180 in phase opposition;

first control means for providing a time control signal;

a first drive circuit connected to said first control means and one end of said center tapped primary winding to provide a driving current for a period of time determined by said first control means;

second control means connected to said first control means and operative upon said first control means becoming inoperative to provide a control signal having a predetermined time duration;

a second drive circuit connected to said second control means and to the other end of said center tapped primary winding to provide a drive current therethrough to said center tap;

3,358,216 5 6 a unilateral current conducting device connected to References Cited one end of said second secondary winding; and UNITED STATES PATENTS an impedance connected to the other end of said second secondary winding and to said unilateral cur- 3,069,612 12/1962 Hamilton 3O7 106 X rent conducting deviw 5 3,088,075 4/1963 Pintell 328-65 X 8. The apparatus of claim 7 wherein said first and 3,109,106 10/1963 JaFOSIk et 307 88'5 second control devices are singleshot multivi'brators. 3,297,954 1/1967 Wlley 33152 9. The apparatus of claim 7 wherein said unilateral current conducting device is a diode. JOHN COUCH Prlmary Exammer 10. The apparatus of claim 7 wherein said impedance 10 W. E. RAY, Assistant Examiner. is a resistor. 

1. APPARATUS FOR GENERATING HIGH VOLTAGE PULSES COMPRISNG: A TRANSFORMER HAVING A CORE WOUND WITH A PRIMARY WINDING AND FIRST AND SECOND SECONDARY WINDINGS, SAID FIRST AND SECOND SECONDARY WINDNGS BEING WOUND 180* IN PHASE OPPOSITION; A CLAMP CIRCUIT CONNECTED IN SERIES WITH SAID SECOND SECONDARY WINDING TO FACILITATE PRESETTING THE CORE FLUX, SAID CLAMP CIRCUIT INCLUDING AN IMPEDANCE FOR DISSIPATING ENERGY; AND MEANS CONNECTED TO SAID PRIMARY WINDING FOR DRIVING CURRENT THERETHROUGH FIRST IN ONE DIRECTION TO PRESET SAID CORE FLUX WHEREBY CURRENT FLOWS THROUGH SAID SECOND SECONDARY WINDING UNDER CONTROL OF SAID CLAMP CIRCUIT AND THE ENERGY IS DISSIPATED BY SAID IMPEDANCE, AND THEN IN AN OPPOSITE DIRECTION TO CAUSE A CORE FLUX CHANGE TO PRODUCE A HIGH VOLTAGE PULSE ACROSS SAID FIRST SECONDARY WINDING, SAID CLAMP CIRCUIT THEN BEING OPERATIVE TO PREVENT FLOW OF CURRENT THROUGH SAID SECOND SECONDARY WINDING. 